Which BABOK task determines the validity of solution measures in place?

The task that determines the validity of solution measures in place is "Measure Solution Performance." This activity involves evaluating how well a solution is functioning against predefined performance measures and metrics. By assessing these measures, business analysts can determine if the solution is meeting its intended objectives and delivering the expected benefits. This task requires collecting data, analyzing results, and comparing them against the established benchmarks to ensure that the solution is performing effectively.

In the context of this question, while the other options are related to performance and requirements, they do not specifically focus on measuring the actual performance outcomes of the solution. "Analyze Performance Measures," for instance, refers to interpreting the data collected about performance but does not itself provide the ongoing evaluation of whether those measures are accurate or relevant. "Assess Change Impact" deals with understanding the implications of changes on the organization or stakeholders, rather than measuring performance. "Define Requirements" focuses on establishing what needs to be delivered rather than assessing how well it performs post-implementation. Thus, "Measure Solution Performance" directly relates to validating solution measures and is the most appropriate choice.